1. Field of the Invention
The present invention relates to a dual-axis hinge and, especially, to a dual-axis hinge mounted between a cover and a base of a portable device to allow the cover to be pivoted relative to the base.
2. Description of the Prior Arts
With the progress of the technology, conventional portable devices have different types. Tablet personal computers become the mainstream of the portable devices. To minimize the volume, the manufacturers consider developing foldable tablet personal computers.
U.S. patent publication No. 2008/0307608 and U.S. Pat. No. 7,140,074, which are incorporated herein as references, both disclose a conventional hinge with gears. The conventional hinge has two gears to allow the cover to pivot relative to the base. The disadvantage of the conventional hinge is that the conventional hinge covers a part of the screen, since the conventional hinge is mounted in the middle of the cover and the base. Therefore, when the cover is opened relative to the base, the screens on the cover and the base cannot be continuous as a whole screen. Then, the conventional hinge is not capable of being used in tablet personal computers.
Furthermore, the conventional hinges in the aforementioned references have another disadvantage. When the cover is closed relative to the base, the conventional hinge is at an included angle of 90 degrees respectively with the cover and the base (as shown in FIG. 11 of US Patent Publication No. 2008/0307608). The two gears have the same diameter and teeth number so that the thicknesses of the cover and the base have to be the same. If the cover is thinner than the base, the gear connecting to the cover protrudes out from the top or bottom surfaces, especially the top surface. Then, the portable device has an uneven surface and results in an unpleasant appearance.
Moreover, with reference to FIG. 10, when the cover 70 is closed relative to the base 80, the conventional hinge is at included angles that are not equal to 90 degrees with the cover and the base. Then, the gears 91, 92 having the same diameter are not applicable. For example, if the conventional hinge is at an included angle of 50 degrees with the base 80, the conventional hinge is at an included angle of 130 degrees with the cover 70. Since the gears 91, 92 are the same, the gears 91, 92 have the same teeth number. When the cover 70 is opened and the first gear 91 is rotated at 90 degrees, the second gear 92 is also rotated at 90 degrees as shown in FIG. 11. Then, the top surfaces of the cover 70 and the base 80 do not align with each other and form a drop. Therefore, the conventional hinge is not applicable for tablet personal computers.
To resolve the aforementioned problems, the gears need to have unequal diameters and teeth number to maintain an equal rotating rate. Although the conventional hinge with the gears having different diameters may be used for the portable devices with the cover and the base having different thicknesses, the conventional hinge with gears having different diameters cannot be used in portable devices with the cover and the base having the same thicknesses.
Thus, the conventional hinges with gears cannot be utilized in portable devices having different specifications.
To overcome the shortcomings, the present invention provides a dual-axis hinge to mitigate or obviate the aforementioned problems.